Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TerryD on March 25, 2017, 11:12:08 am

Title: Fender PA 100 Master Volume = Blessing or Curse?
Post by: TerryD on March 25, 2017, 11:12:08 am

I've done a lot of work on this and still am not sure it sounds that good.  Black faced the PI section ala Gerald Weber for a 64 twin sound.  Redid the tone sections except the volume controls which seemed like too much work but I'm going to switch them from 250 to 1 meg now and switch the cathode bypass caps from 25mfd (tried 10 and 4.8 also) to .68.

Does that seem good?  Anything else I can do?  Quick tips how to do ideas is helpful as well.

OK I see the Master Volume goes "into" the 12AT7 PI tube.  That's got to make everything sound less than stellar, doesn't it?  But a master on a 100 watt amp has got to be handy, doesn't it?  Any resolutions???  I have a Sholtz power soak, maybe I should use that?

Thanks,Terry

Title: Re: Fender PA 100 Master Volume = Blessing or Curse?
Post by: zapped on March 25, 2017, 10:15:39 pm

I was given a PA 100 Reverb years ago and tried it as a guitar amp . I later learned it used the same transformers as Twin Reverb so after many long hours and dollars I have a Twin Reverb. I used a Weber chassis and fiber board. I love its sound and great reverb but never got a working tremolo. It was my first build and a true challenge. I did leave out the master volume to keep it all Blackface flavor. I did find most of the pots were not usable in a Twin Reverb.. Good luck with your project. 

Title: Re: Fender PA 100 Master Volume = Blessing or Curse?
Post by: TitaniumValhalla on March 27, 2017, 02:15:40 pm

I had a PA135 which was the same amp but with even bigger transformers. Over the years I made a lot of the same kind of changes you are talking about and eventually gave up because I could just never get it to sound as good as a Fender should. I know when I was doing research on it a lot of people's answer to these amps is to just sell them to someone who wants gigantically loud and sterile cleans, and over time I came to agree with that assessment. In my case I refused to get rid of the amp because I've had it since I was a teenager but I did gut the chassis and put a superior circuit in it. I still have the old transformers and might do something with them someday, or use them for boat anchors.